Procedure:
It doesn't take much to start the freezing process. Read through the entire
procedure and predict what will happen.

Prediction:

Place 2 ml water in test tube.

Weigh out 15 grams of sodium thiosulfate and put 4 crystals in the
water in the test tube.

Create a saturated solution at room temperature, stirring and adding
more crystals until no more will dissolve.

Gently heat the solution, adding the remaining crystals until all have
been dissolved in the test tube. Be sure that no undissolved bits of sodium
thiosulfate remain in the test tube.

Place the test tube in a beaker of cool water so the solution can cool
to room temperature without moving.

When the solution still is as clear as water but the test tube feels
cool to the touch, you have created a supersaturated solution.
This solution is a liquid at a temperature below where it normally becomes
a solid.

Carefully lift the test tube out of the beaker of water and feel the
temperature of the lower half of the tube.
How does it feel?

Drop one crystal of sodium thiosulfate into the test tube and watch
what happens. Feel the temperature of the lower half of the test tube as
the change takes place. Record your observations.